Factor VIII related antigen in the assessment of vasculitis

SUMMARY Factor VIII related antigen, an endothelial cell product, was markedly raised in systemic necrotising arteritis, reflecting disease activity, but was not raised in active cutaneous vasculitis. In rheumatoid arthritis high levels were only found in systemic vasculitis or Felty's syndrome, but in other connective tissue diseases increased levels were more frequently detected and usually related to disease activity. It did not correlate with C reactive protein. It was also raised in non-inflammatory peripheral vascular disease and after surgery and was not specific for vasculitic endothelial damage. Factor VIII related antigen may be useful in identifying and monitoring systemic necrotising and large vessel arteritis. Key words: von Willebrand's factor, C reactive protein, endothelium, arteritis, Wegener's granulomatosis, periarteritis nodosa, connective tissue diseases, rheumatoid 'arthritis, ischaemia. Vasculitis may arise de novo or as a feature of various connective tissue diseases, ' its consequences depending on the size, site, and number of blood vessels affected.2 Diagnosis is difficult and may require invasive investigation. Small vessel vasculiti